The number of people charged in the ring now stands at 23, Medford police Lt. Mike Budreau said.

"This is by far the largest mail theft ring we've seen in Medford," Budreau said. "You're looking at over 1,000 victims in this case who had their mail and identities stolen."

The investigation sparked last spring when Medford police and the U.S. Postal Inspection Service uncovered a ring of thieves taking mail and using identifying documents found there to open new bank accounts, write fraudulent checks and get credit and debit cards.

Police said more than 2,000 pieces of stolen mail from 1,000 different victims were documented in the investigation.

Investigators were able to track down the ringleaders and steer them into the federal system, Budreau said.

"That was a real victory because the federal penalties are stronger," Budreau said.

Federal prosecutors indicted Eduardo Navarro, 24, Dallas Lee Tedford, 32, Robert Powelson, 29, Kayla Strange, 23, and Lana Lorraine Marshall, 29, in early May, alleging that they stole large quantities of mail between September 2012 and March 2013. All are currently in custody awaiting trial.

Since then investigators have spent months tracking down co-conspirators.

The suspects were loosely connected, often brought into the group and paid cash to open fraudulent bank accounts, Budreau said.

"They would bring in a new member and pay them 200 bucks to open an account," Budreau said. "They would then deposit money and checks stolen from the mail and immediately go out and spend it."

One strategy the suspects used time and again was to open a fraudulent account and apply for an ATM card. They would then run up as many charges as they could before the bank flagged the account as suspicious, Budreau said.

"Once the bank put a hold on the account they would simply move on to open another account," Budreau said.

Medford police presented the case to a Jackson County grand jury in June, identifying 13 people suspected of working with the alleged masterminds who were already facing federal charges. Five of them were arrested in recent weeks, and officers rounded up six more Wednesday, Medford police said. Police are still looking for the last two of those suspects.

Investigators also arrested five other suspects during the course of the investigation.

Two other suspects were arrested on misdemeanor second-degree theft charges.

The suspects who face federal prosecution could receive sentences ranging from five to 30 years in prison, with mandatory minimum sentences of two years for aggravated identity theft convictions, according to federal authorities.

"We have put hundreds if not thousands of hours into investigating this case and there is more to come," Budreau said.